Transforming vulcanized styrene-butadiene waste into valuable raw material: An opportunity for high impact polypropylene production

Abstract

The vulcanized residue of styrene-butadiene rubber (SBRr) is a raw material with potential for re-addition in the production chain, adding value and reducing environmental impact. Polypropylene (PP) compounds with SBRr from the footwear industry were produced, adding styrene-(ethylene-butylene)-styrene (SEBS) as compatibilizer, with 20% ​​and 30% of styrene (St.). Addition of 30% SBRr did not compromise the processability, since the torque and flow index increased slightly. Significant increases in impact strength were achieved for PP/SBRr/SEBS (10% -20% St.) and PP/SBRr/SEBS (10% -30% St.), with gains of 316% and 248%, related to PP. The elastic modulus, tensile strength, elongation at break and Shore D hardness indicated greater flexibility for the PP/SBRr/SEBS, especially in the copolymer with 20% St. The thermal deflection temperature (HDT) indicated that even adding high content of SBRr to PP, the HDT was not severely affected, possibly due to its crosslinked character. PP/SBRr compatibilization with SEBS (20% St.) inhibited the PP crystalline peaks, as verified through X-ray diffraction (XRD). Stable morphology was achieved upon 10% of SEBS addition to PP/SBRr, providing proper interfacial adhesion and fine particles, contributing to toughen PP. Acquired results are promising for the rubber recycling, aiming at the production of high-impact polypropylene for containers and furniture accessories applications.